This invention relates to a combinatorial weighing apparatus for processing a number of different articles using a variety of different target weights, wherein the conditions necessary for combinatorial weighing are reserved and registered in advance and the reserved values are called from memory whenever a weighing operation is performed, thereby making it unnecessary to set the weighing conditions each time.
A combinatorial weighing apparatus known in the art has a plurality of weighing machines. Combinatorial weighing is carried out by weighing articles which have been supplied to the weighing machines, computing combinations of the obtained weight values, selecting the combination of weighing machines (referred to as the "optimum" combination) that gives a total combined weight value equal to a target weight value or closest to the target weight value within preset allowable limits, discharging only those articles contained by the selected weighing machines, and subsequently replenishing the emptied weighing machines, i.e., those which have discharged their articles, with articles to prepare for the next weighing cycle. The foregoing sequence of steps is repeated to carry out a continuous, highly accurate weighing operation automatically.
FIG. 1 is a side view, partially in section, of a combinatorial weighing apparatus of the above-described type. Numeral 1 denotes a dispersing feeder for dispersing articles radially outwardly to supply the articles to n-number of radially extending weighing sections arranged around the dispersing feeder 1. The feeder 1, which is of vibratory conveyance type, is caused to rotate back and forth and reciprocate vertically in rapid, oscillatory fashion by a vibrator 2 incorporating an electromagnet, whereby the articles are conveyed distributively to each weighing section.
Each weighing section comprises a supply troughtype feeder 3, a pool hopper 5, a weighing hopper 6, and a weight sensor 7. The weighing hopper 6 and weight sensor 7 in each section constitute a weighing machine.
Each supply trough feeder 3 is vibrated by a vibrator 4 incorporating an electromagnet, so that the articles received from the feeder 1 will migrate along the trough and drop into the corresponding pool hopper 5. Each pool hopper 5 is provided with a pool hopper gate 8 which, when opened, releases the articles from the hopper 5 into the corresponding weighing hopper 6. Each weighing hopper 6 is attached to the corresponding weight sensor 7. The latter measures the weight of the article batch supplied to the weighing hopper and applies the measured weight value to a combinatorial computation control unit (not shown in FIG. 1). The control unit, based on the weight values received from all of the weight sensors 7, computes all possible combinations of the weight values and selects the optimum combination, namely the optimum combination of weighing machines mentioned above. The control unit then delivers an article discharge signal to the selected weighing machines, causing weighing hopper gates 9 of the weighing hoppers 6, corresponding to the selected weighing machines, to open and discharge their articles into a common underlying collecting chute 10. The articles are collected at the bottom central portion of the chute 10 and then delivered to a packaging machine (not shown). Numeral 11 denotes a drive unit for opening and closing the hopper gates 8, 9 of the corresponding weighing section.
In order to prepare for an automatic weighing operation using the above-described combinatorial weighing apparatus, it is necessary to decide the conditions that are to hold for each weighing operation and then enter the relevant numerical values into the control unit of the apparatus using input means such as numeric keys, digital switches or dial switches.
Ordinarily, the entered weighing conditions, namely the set numerical values, constitute at least the following values. First, there is the target weight value (hereinafter referred to as the "target value") serving as the target of the combinatorial weighing operation. Then there are upper and lower limit values which bracket the target value for defining an allowable range within which a total combined weight value obtained from the combinatorial computations must fall, in order to have an acceptable accuracy. Finally, there are values for adjusting the amount of articles supplied to each weighing machine. More specifically, these are values, in the form of numerical codes, that specify the vibration conditions for the distributing feeder 1 and supply trough-type feeders 3, namely the amplitude and duration of vibration.
Adjustment of the amplitude of vibration of the dispersing feeder 1 and supply trough feeders 3 in order to control the amount of articles supplied, is achieved by regulating the magnitude of the current flowing into the electromagnet of each feeder. Adjustment of the duration of vibration of these feeders is performed by a timer. In order to initially set the amplitude and duration of vibration to appropriate values, the prior-art practice is to first set the amplitude and duration of feeder vibration to provisional values by dial switches or the like, and then perform a trial weighing operation by supplying articles on the basis of these set provisional values. It is of course necessary to preset the target value, upper limit value and lower limit value using digital switches. At the end of the combinatorial computations, the number of weighing machines selected as the optimum combination appears on a display. The dial switches are then adjusted in such a manner that the displayed number, i.e, the number of selected weighing machines, will be one-half the total number of weighing machines, i.e., n/2. The reason is that the combinations made up of n/2 machines are the largest in number, so that this grouping of combinations will likely afford combined weight values closest to the target value. The vibration amplitude and duration values set in this manner will be the appropriate values. When the setting of all weighing conditions has been completed, an actual combinatorial weighing operation may begin.
Thus, the foregoing conditions (namely the vibration amplitude and duration) for weighing out articles are set by a trial and error method and, whenever the kind of articles or target value changes, the operator must reset these conditions each time, using the digital or dial switches, in accordance with the article kind, target value and upper and lower limit values.
There are situations where it is desired to change the weighing conditions with some frequency, as when weighing out many different kinds of articles or when using a number of different target values. At times it is even desired to change the weighing conditions in accordance with the season and load, etc., even for articles of the same kind. Obviously, resetting the weighing conditions each time is a troublesome task requiring an experienced operator. Moreover, when there are a large number of weighing conditions to be set, there is a greater risk of error and a decline in productivity.